Railroad-wheel operated controlsignal generator



Aug. 6, 1968 c. A. GALLAGHER 3,396,271

RAILROAD-WHEEL OPERATED CONTROL-SIGNAL GENERATOR Filed March l5, 1967TTORNE United States Patent O 3,396,271 RAILRGAD-WHEEL OPERATED CONTRGL-SIGNAL GENERATOR Cornelius A. Gallagher, Syosaet, N.Y., assignor toServo Corporation of America, Hicksville, N.Y., a corporation of NewYork Filed Mar. 15, 1967, Ser. No. 623,253 5 Claims. (Ci. 246-249)ABSTRACT OF THE DISCLOSURE This invention is concerned With a particularinterconnection of two magnetic-induction wheel-trip devices capable ofresponding to railroad-wheel movement and so interconnected as toeffectively nullify or buck-out spurious signals induced by electriccurrents passing down the rails, as in electrified territory. Thearrangement is such that not only are the spurious signals eliminated,but a control signal is developed in a polarity which is insensitive tothe particular direction of traffic passing the wheel-trip location.

This invention relates to a particular forni of signal generator for usein conjunction with railroad tracks to enable the automatic generationof a control signal based on the instant when a moving railroad Wheelpasses the detection region.

Devices of the character indicated include magnetic-induction deviceswherein a polarized air gap is established at the rail, the reluctanceof the gap being modified as the wheel or its flange effectively changesthe physical proportions of the air gap. An electric coil linked to themagnetic core develops an Output voltage characterized by a first swingof one polarity, followed by a similar swing of opposite polarity, aswhen the wheel flange enters and then (later) leaves the gap.

In electrified territory, heavy electrical currents passing down therails may induce undesirable spurious responses from suchmagnetic-induction wheel trips, and it is desirable etfectively t-oneutralize such responses while at the same time providing a suitabletime-identifying controlsignal output to mark the passage of each wheel.lt is desirable that such control signals be of the same polarityregardless of the direction of traflic movement past the detectionpoint.

It is, accordingly, an object of the invention to provide an improveddevice of the character indicated lending itself particularly to use inelectrified territory and accommodating itself inherently to traffic,regardless of the direction of traffic movement.

Another object is to meet the foregoing objects with a device having aninherent capacity to produce the same apparent control signal outputrregardless of the direction of tratlic movement.

A further object is to meet the foregoing objects with a deviceproducing a control-signal output magnitude greater than that producedby prior wheel trips and uniquely identifying an instant of time when awheel center is passing.

A general object is to meet the foregoing objects with a structure whichis inherently simple, which is a passive in the sense that it requiresno external source for derivation of basic signal inputs, and which mayutilize existing components to the largest extent possible.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a -readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show for illustrative purposes only,preferred forms of the invention.

3,396,271 Patented Aug. 6, 1968 ICC FIG. 1 is a diagram schematicallyshowing electrical components of one form of the invention shown inapplication to a section of railroad track;

FIG. 2 is a series of graphs depiciting, on the same time base, voltagefluctuations encountered in the operation of the device of FIG. l; and

FIG. 3 is a simplified diagram showing a modification of FIG. 1.

Briefly stated, the invention contemplates the employment of twomagnetic-induction wheel-trip devices of the variety which haveheretofore been bolted to a rail so as to enable characteristic outputpulses to be generated to mark the instant of time when a railroad wheelpasses the wheel-trip location. The two trips, in the present case, arespaced from each other by an amount so related to wheel diameter thatthe flux in the air gap for one of the trips is undergoing its greatestchange due to a given wheel-flange entering that gap, while flux in theother wheel trip is undergoing its greatest change due to the sameflange leavn'g the latter gap. The number of turns on the output coilsof both these devices are matched and connected so that their outputvoltages normally buck or balance out.

The circuitry for generating a suitable control signal includes therelay responsive to the thus-combined outputs of the two coils, and thisrelay produces an output signal of the same polarity for each passingwheel, regardless of the direction of passage of the wheel.

Referring to FIG. 1 of the drawings, the invention is shown inapplication to a railroad rail 10 having a head 11 on an upstanding weband resting on a flat base 13. Two permanently polarized magnetic cores14-15 are mounted adjacent the web and beneath the head 11 so that theouter poles 16-17 of each core are spaced laterally to generally thesame extent with respect to the head and web 11-12 of the rail.Longitudinally, the cores 14-15 are spaced a distance D. Separate likeoutput coils 18-19 are linked to the respective cores 14-15 and are sointerconnected that for simultaneously induced voltages due to the samecause, these output voltages buck out or are self-cancelling. In theform shown, both coils 18-19 have turns in the same direction and,therefore, their output connections are opposed.

The parts thus far described may be all combined within a singleassembly suggested by phantom outline 20 of generally rectangularprismatic form, being preferably a plastic potting fully sealing andenclosing the coils and their cores, the potting being secured by means(not shown) to the web section of the rail. In this circumstance theoutput of the assembly may be contained in a single two-conductor cable,suggested by the loop 21.

The spacing D is determined by considerations of greatest flux change inthe respective magnetic circuits due to passage of particular railroadwheel, it being understood that railroad wheels are of magnetic-fluxconducting material. In the form shown, the variety of wheel-tripelement suggested at 14-15 is such that the polarized air gaps aredefined between the outboard pole faces 16-17 and the nearest adjacentedge of the head 11 of the rail. These polarized gaps are located on theinside of the rail and are poised to undergo marked change in reluctanceas wheel flanges of passing wheels enter and leave the polarized airgaps. In the event of such wheel-flange operated devices, the spacing Dis such that the wheel flange for a given wheel is entering thepolarized gap for ore wheel trip while it (the same wheel flange) isleaving that for the other. The significance of this relationship willbe explained in conjunction with curves a and b of FIG. 2.

Assume a wheel on the rail 1t) and moving from left to right. Its flangewill first change the reluctance of the polarized gap associated withcore 14, and the direction of this change may be such as to induce afirst voltage swing 25 in a negative polarity in the output of coil 1-8.The wheel will progress down the track until a time comes when the angeleaves the polarized gap associated with core 14, at which time the samecoil 18 will develop a similar but oppositely poled voltage swing 26 inits output.

In the same manner, the same wheel flange will induce rst a negative andthen a positive voltage swing in the output of coil 19 in connectionwith traversal of the polarized gap associated with core 15. However,due to the bucking or opposed-phase connection of the outputs of coils18-19, the sequence of pulse outputs at coil 19 for the same wheel-angewill appear to be of polarity opposed to that of coil 18. Thisrelationship is suggested in curve b of FIG. 2, wherein the iirst pulseat the output of coil 19 is shown as being electively a positive pulse27 and is followed by a negative pulse 28, as the wheel ange leaves thepolarized gap associated therewith.

Now, in electrified territory where track currents may be severe, as dueto operation of electric traction locomotives, a given current in thetrack may induce a voltage in the outputs of coils 18-19. However, thevoltages thus induced at coils 18-19 will be simultaneously induced andbecause of the similarity of the coils to each other these voltages wllbe equal and opposite. This relation being suggested by a dashed outlinegraph 29-30 at FIG. 2A.

The net result is to neutralize such rail-induced voltages and todiscriminate for pulses due to wheel-ange passage, it being noted thatthe pulses 26-27, due to the same ilange leaving the gap associated withcore 14 while it is also entering the gap associated with core 15, areeffectively simultaneous and of the same polarity. Thus, due to theinterconnection already described for the coil outputs, these outputscombine additively to produce a pulse substantially exceeding the outputof either one of the coils 18, and amounting to substantially double theoutput of either coil.

The additive response is suggested at curve c for the assumed conditionof the wheel moving from left to right in the sense of FIG. l. Thisresponse is seen to comprise the rst negative swing 25 associated withcoil output at 18, followed by a double-amplitude central pulse 31representing the combined outputs 26-27 from both coils, and terminatedby another lesser-magnitude negative pulse 28, representing that due tothe ange leaving the polarized gap associated with core 15.

For trai-lic proceeding in the opposite direction along the rail 10, thepolarized gap associated with core is the one rst to be traversed. Asimilar pattern of signalpulse development will occur as the wheelproceeds into and beyond the distance D, but due to the opposed-phaseconnection of the outputs of coils 18-19, the combined output-pulsepattern will be the mirror image of that described at FIG. 2c for thecase of left-to-right tratiic movement. Curve d of FIG. 2 suggests thismirror-image pattern, being characterized by a rst minor positive pulsefollowed by a double-amplitude negative pulse 31', and ending withanother minor positive pulse 28'.

The present invention concerns itself with accepting either one of thepulse patterns displayed at curves c and d of FIG. 2 and derivingtherefrom a control pulse which is unrelated to the particular polarityof the pattern at FIG. 2c or 2d. Specifically, if desired, thecontrol-pulse output from my circuitry can be of positive polaritywhether or not the input pulse pattern is that displayed at FIG. 2c orFIG. 2d.

FIG. 2e represents one such control pulse (of positive polarity) whichmay for certain specific control purposes be adequate, and which willcertainly be generated, regardless of whether the input pulse pattern isthat of FIG. 2c or that of FIG. 2d. Such an output pulse is generated bythe circuit of FIG. 3.

In FIG. 3, the two spaced cores 14-15 are schematically shown, togetherwith their associated output windings 18-19 connected in phaseopposition. The combined outputs of these coils are connected by linesto a polarized relay having an actuating coil 36 and an armature 37movable between interconnected 4lrst and second (e.g., front and back)contacts 38-39. These interconnected contacts form part of a circuitincluding a suitable source 40 and the armature 37 to provide an outputin line 41 to a utilization device, which may be the input relay for aroadtraic grade-crossing gate or the like.

In operation, the polarized relay will function to produce threediscrete and closely associated successive output pulses in line 41,namely the pulses 42-43-44 of the same polarity. Strictly speaking, asmall time interval (suggested by dashed lines 45-46) will interrupt orintervene between pulses 42-43-44, but it will be understood that themechanical and inductive yinertia of the control relay of theutilization device will effectively ignore these short interruptions sothat the net result of signal-development in line 41 to effectivelyproduce a single elongated pulse 42-43- 44, of single polarity,regardless of direction of wheel movement.

In other applications, it is important that there be betteridentification of the instant of time when the wheel center for eachpassing wheel is passing a given location on the track, and in thepresent case the ldescribed interconnection of wheel trip components forthe spacing D enables this instant of time to be identiiied when thewheel center is substantially midway along the distance ID, as suggestedby the D/Z designation in FIG. l to identify the longitudinal locationX. The circuitry shown in HG. l enables substantially this instant oftime to be identied.

In the circuit of FIG. 1, the ultimate device to be controlled oroperated is `designated at 50 and denominated a relay or gate. It maythus represent the gate-opening (or the gate-closing) function for ahotboX-detector circuit, as of the variety shown and described ingreater detail in U.S. Patent No. 2,880,309.

Control circuitry for the signal supplied to relay 50 is such as toeffectively ignore or exclude the minor opening and closing pulses foreach wave train, regardless of the direction of passing tratiic, and onthe other hand to accentuate and respond essentially only to the doubleamplitude central pulse 31 (or 31') regardless of the direction oftraflic.

For this purpose, the control-signal circuitry may utilize adouble-throw relay 51, having rst and second contacts (front and back)determining a rst direct input connection 52 (to output 55) and a secondinput connection 53 (to output 55) based on the combined outputs ofcoils 18-19. The input connection 53 is shown with an inverter 54 sothat the polarity of signals in lines 52 and 53 is always in opposedphase. For purposes of simplifying discussion the legend '.E has beenemployed to suggest that the line 52 accommodates eastbound traffic(left to right in the sense of FIG. 1) while W suggests that line 53accommodates westbound traine, this accommodation function contemplatingthe particular instantaneous connection of front or back contacts atrelay 51. The particular actuation of relay 51 will be described, but itassures that regardless of the direction of passing tra'ic, the output55 of relay 51 will be characterized by pulse trains in which thecentral pulse attributable to eastbound double-pulse development 31 orto westbound doublepulse development 31 will appear in the samepolarity, so that a half wave rectifier 56 may electively cut oiminor-pulse components and thus accentuate just the double-pulsecomponents.

'For eastbound traffic, let it be assumed that the relay 51 has a normalposition establishing direct connection of rectier 56 to the line 52.-In that event, there is no need to operate relay 51, and rectifier 56is eiective to select the double-pulse positive swing 31 for anidentification of the instant of time at which the Wheel center passes'location X, so that relay or gate 50 may respond in synchronism withthis determination.

On the other hand, for westbound tratiic, the desired double-pulseamplitude 31' is of undesired polarity, so that the relay 51 must beoperated to invert the pulse 31'. To achieve this operation in the formshown, a suitable poled amplifier 60 responds to the initial positiveminor pulse 25', signifying a westbound signal development to actuatethe first of two inputs 61-62, to a bi-stable multivibrator 63. Thisfirst input 61 will be understood to be operative to change the state,say from a first state in which relay 51 is not operated to a secondstate in which relay 51 is operated. The second input connection 62 tomultivibrator 63 is shown connected to a reset circuit which will bedescribed. (The reset function is generated as a marker of thetermination of the trip pulse wave train generated for each wheelpassing the distance D.)

In the `form shown, the reset pulse is developed by -a full-waverectifier 65 responding to the combined outputs of coils 18-19. Therectifier output is shaped at 66 into an elongated square Wave which maybe of the nature shown at 42-43-44 in curve e of lFrIG. 2, whichconstitutes one single square wave of this duration. The square-waveoutput from circuit 66 may be differentiated at 67 to develop a pulse ofunique polarity to mark the end 0f the square-Wave. A poled diode 68 isshown selecting this response and therefore developing a reset pulse inline 69 to return multivibrator 63 to its normal first state, at whichtime relay 51 will be de-energized, thus restoring connection ofrectifier 56 to the input line 52.

In order that the first negative minor pulse 25 for eastbound trafiicshall be ineffective to `operate the multivibrator 63, -I show alock-out circuit for biasing the amplifier 60 below cut-ofi in thiscircumstance. The lock-out circuit is shown to include a poled diode 70connected to the combined outputs of coils 18-19 and selective torespond to the initial negative swing 25 for a wave train attributableto eastbound traffic. Diode 70 then supplies to a second bi-stablemultivibrator 71 a first control signal determining change of state toeect a cut-oli signal in line 72 to amplifier 60.

Multivibrator 71 will remain thus actuated in spite of succeeding pulsesfrom diode 70 until a reset pulse in line 73 (to the other inputconnection of multivibrator 71) is operative to again change the stateof multivibrator 71, thus restoring amplifier 60 to its originaloperative condition.

It will be seen that I have described an inherently simple connection ofmagnetic-induction wheel-operated devices which is inherentlyself-compensating for railinduced currents, but which on the other handis operative to generate control signals of a given polarity, regardlessof the direction of passing traiiic. These control signals may be sorefined in terms of the timing of their development as to utilizeinherent signal-to-noise enhancement attributable to the spacing D forwheel passage, and to inherently effectively split the distance D forwheel-center identification.

What is claimed is:

1. Control means responsive to trafiic movement along a railroad track,comprising two rail-mounted magnetic wheel-trip devices secured inspaced relation along the same track, each of said devices presenting amagnetized air gap for interception of a wheel ange, the spacing betweensaid trips being such that a Wheel ange on a given axle is leaving thegap for one wheel trip as a wheel fiange on the same axle is enteringthe gap for the other wheel trip, each of said wheel-trip devicesincluding an electrical output coil, said coils being connected inphase-opposition, whereby signals induced in said coils due to railcurrents are effectively bucked-out, whereas a passing railroad Wheelange will induce output-coil voltages which are additive for theentering pulse of the second-traversed trip and the leaving pulse of thefirst-traversed trip, and connecting means including a relay responsiveto the thus-combined output of said coils, said relay producing anoutput signal of the same polarity for each passing wheel regardless ofthe direction of passage of the wheel.

2. Control means according to claim 1, in Which said relay is apolarized double-throw relay with inter-connected front and backcontacts, and a control-signal output circuit including a voltage sourceand the inter-connected contacts of said relay.

3. Control means according to claim 1, in which said relay is of thedouble-throw variety having front and back contacts and an outputcircuit including an armature normally engaging one of said contacts tothe exclusion of the other, first and second connections of saidcontacts to the combined output of said coils, one of said connectionsto one of said contacts being of inverted polarity with respect to theother of said connections to the other of said contacts, and actuatingmeans for said armature including polarity-sensitive connection to thecombined output of said coils.

4. Control means according to claim 3, in which said polarity-sensitiveconnection includes a bi-stable multivibrator having an output connected`for operation of said re'lay, said multivibrator having a first statewhich is inoperative to actuate said relay and a second state which isoperative to actuate said relay, said multivibrator having a first inputconnection for actuation of said multivibrator from said first to saidsecond states and having a second input connection for actuation fromsaid second to .said first state, means responsive to a first polarityof combined coil signal output and connected to said first inputconnection, said last-defined means including means responsive to anopposite polarity of combined signal output voltage and effective tolock-out operation of said polarity-sensitive means, and reset means forsaid multivibrator connected `to said second input connection thereofand including means detecting completion of each detected wave train inthe combined output of said coils.

5. Control means according to claim 4, in which said reset meansincludes a full-Wave rectifier connected to said combined signal output,wave-shaping means associated with said rectifier for developing anelongated square wave for wave train in said output, and differentiatingmeans connected to said wave-shaping means.

References Cited UNITED STATES PATENTS 3,281,593 10/ 1966 Mendelsohn246-249 3,359,417 12/ 1967 Gallagher 246-249 FOREIGN PATENTS 730,359 5/1955 Great Britain. 1,147,728 6/1957 France.

ARTHUR L. LA POINT, Primary Examiner.

S. T. KRAWCZEWICZ, Assistant Examiner.

